Socket contact



April 24, 1951 v A. w. FRANKLIN 2,550,237

SOCKET CONTACT F iled June 14, 1947 2 Sheets-Sheet l I INVENTOR. TEL:1 5 ALBERT w. FRANKLIN A.. w; FRANKLIN April 24, 1951 SOCKET CONTACT 2 Sheets-Sheet 2 Filed- June 14, 1947 INVENTOR. ALBERT W. FRANKLIN I Patented Apr. 24, 1951 UNITED STATES PATENT OFFICE; 2,550,237 SOCKET CONTACT Albert w; Franklin, New York, N. Y. Application June 14, 1947,. Serial: No.. 754,vo

contacts as used as apart of sockets or connectors by means ofwhich electrical devices may be detachably engaged and supported.

, ,An object of thisinventionis to provide an.

improved form of tubular contact. adapted to easily receive and tenaciously retain the terminal pins of electrical devices such as vacuum tubes, condensers. transformers and the like.

Another object of this invention is to provide an.: improved contact of this type into which the terminal pins of the device to be mounted and connected. may-be relatively easily inserted but which are relatively hard to withdraw.

A still further object of. the invention'is to provide .an improved cont-act of this type which 3 simultaneously firmly grips theterminal pins mechanicallyand establishes good electrical contact therewith. V r i Amore specific object of the invention is to provide in such contacts a cutting or biting edge for establishing goodelectrical contact upon insertion of the terminal pins. 7

,. Another object of the invention is to provide a contactwhich will provide good mechanical and 1 Claim. (Cl. l 7 .3328) 'This invention comprises improvements in I pin inserted; and

Figure .9 is an enlarged cross sectional view on the diameter of the bar-rel portion of thecontact looking towards the terminalwing. I

Figures 1 and 2 illustrate somewhat diagrammatically the type. of socketin which the contact electrical connection with a terminal pin upon repeated insertion and removal thereof.

An overall object of the inventionis to provid a contact having these qualities for use with electrical devices having small terminal pins such as, for-example, those used on miniature vacuum tubes where, the terminal pins have a diameter of the order-01 01040 inch.

Another object of..the invention is to provide a contactofthis naturewhich has a terminal pin receiving portion of vbarrel formation having a generally;ball-shaped end to-guide the terminal pin into position to compensate for variations in terminal pin position resulting from manufacturingtolerances, v

. A still further object-of the invention is to pro.-

vide. apincontact which has a high retentivity versus tube insertion force, thereby eliminating additional. means for. locking the terminal pins therein. a q .Qther'andfmore detailed objects; of the inven- 'tion will be apparent from the following disclosure. of the structure .com-prisi ng. this invention. This. invention resides, substantially in the combination, construction, arrangement and relative location of parts, all as will. bePdescrihed in detail, below. I

In the accompanying; drawings,- v Figure; 1 .isatop plan view ofasocket employ- -.plate 2.

of this invention is'commonly-employed. They illustrate a laminated type of socketwhich; is made up of two plates I and'z of suitableinsulating material of suitable configuration. These plates are secured togetherin superposed aligned relation in the particular"structure, i'llustrated by-means of an eyelet 3 and. aresprovided with aligned apertures 4 by means of which the socket may be attached to. a support. These plates are also provided with a series of aligned apertures 5 disposed upon a common radius-and depending innumber upon the number of. terminal pins of the device to be mounted. therein. The barrel portions of the contacts are generally indicated' by the referencelnumeral.;6..and project into and if desiredthrough-the apertures 2" in plate 2 as better seen from Figure 9. ,Plate l hassimilar'apertures '5 aligned with the opposite ends of the barrel portion 6 of the contacts through which the terminal pins]? pass into the contacts- The barriel portions of the contacts are connected to the terminal wings?! by means'of an integral strip 'Tl which lies be- The wings l-extend through rectangular slots, notv shown, in the The contacts are formed-by a series of successive machine operations uponthe edge of a continuous strip S of suitable metal and-the more important of these operations areshown in Figure 3. After several preliminary operations on the edge of the strip there results a lateral extending generally T-shaped part comprising the stem portion TI and the head T. The head. T

is notched out at its outer corners T2 and T3,

is; centrally notched at T4 and is also notched atitspointxof connection with the portion Tl ship as clearly shown in this figure.

gether to form a short slot SI. in the spherical end of the contact meets'the as shown at T5. There results two side extensions T6 and two end extensions T! as clearly shown in Figure 3. A series of holes H are also formed in the body of the strip S in lateral alignment with the lateral formation T. The head T is then formed by a coining operation which works the metal and hardens it, as it is transversely curved, and the flanges T6 and T1 are bent upwardly out of the plane of the figure. The transverse curvature forms the halves TC of the barrel portion of the contact and their cross sectional configuration can best be appreciated from the fourth stage from the right of Figure 3 as well as from Figure 6. The flanges T6 and T1 are not sharply right angles flanges but merge smoothly into the curved halves of the head T as will be apparent from Figures 4 to 9, inclusive.

The next operation is indicated at the third stage from the right of Figure 3 where the two halves of the head have been formed up into a tube slotted at S2 which is defined by the meeting edges of the flanges T6. The flanges T! are presented towards each other as is clear from Figures 5 and 6 to form the spherical or ballshaped lower end of the contact. The cutting edges TB, Figure 7, of the contact are presented towards each other and lie in spaced relation- The ends of the flanges T1 opposite the slot S2 come to- The open slot slots SI and S2 and it will be noted that the shape of these parts is such that a pair of lateral notches TN are formed at the point of the meeting of the open slots sl and S2. These notches provide for some flexibility in the metal at the region of the open slot. This flexibility contributes to ease of insertion and difficulty of withdrawal of the pins while avoiding stressingthe resiliency of the metal to the point where it is permanently deformed. Thus, the .pins may be repeatedly inserted and withdrawn without destroying the resiliency of the structure.

In the next operation, that is, at stage 4, the

barrel-shaped portion of the contact is bent at right angles to the plane of the strip so that the longitudinal axis of the barrel lies at right angles to the plane of the strip. The contact is then cut out of the strip at the next station,

forming the wing 1. It is cut from the strip on the diameter of the outermost hole H as clearly shown in Figure 5. The wing 1 is then bent at 'right angles to the connecting portion Tl, see Figure 4, so as to extend in the same direction and parallel to the barrel portion 6. The contact is now complete.

A seriesof these contacts depending upon the number required are mounted between a pair of the insulating plates l and 2 and they are attached together'by means of the rivet 3, completing the socket. It will be noted that the contact has no wings at the barrel portion as is sometimes used in contacts of this type and is therefore held between the plates by reason of the projection of the Wings 1 and the barrels 6 into the apertures of plate 2 provided therefor and by the connecting portion TI connecting pins are of quite small diameter such as, for ex ample, 0.040 inch. These terminal pins are of course arranged on a common radius and being directly sealed in the glass vessel of the tube are not as accurately aligned in position as they are when molded into a base such as is commonly used for larger devices of this kind. Provision must therefore be made, as is done in the contact of this invention, for guiding the terminal pins into position for full insertion into the contacts, a condition not ordinarily requiring compensation in larger sockets of this kind. This action is clearly illustrated in Figure 9 where the terminal pin is shown entering the barrel portion 6 of the contact misaligned. Its rounded end engaging the ball or spherical shaped lower end of the barrel is guided to the slot at that end for passage thereinto. As it is forced into the slot the barrel portion opens up as illustrated in Figure 8 and the sharp cutting edge TB bites into and scrapes the surface of the terminal pin P so as to out through the oxide normally formed thereon and establish good electrical contact therewith. At the same time good mechanical contact is made in such a manner that the pins are relatively easily inserted but require a relatively considerable force to withdraw them.

The construction illustrated has the very important characteristic that the desired spring tension is maintained by the contact upon repeated insertion and removal of the contact pins.

Similar contacts devised for use with miniature devices such as miniature vacuum tubes have provided a cutting edge with little or no spring action with the result that poor electrical and mechanical contact is established or have provided wiping contact with more spring action but not sufficient pressure and co-action to retain the terminal pins in place. In addition, the wiping contact does not cut through the oxide coating to form good electrical contact.

The outstanding features of this contact are that it is shaped to guide misaligned terminal pins toposition for full insertion, to provide ease of insertion, and adequate mechanical and electrical contact resulting from strong spring action which is retained after repeated insertion and removal of the pins.v The required pressure and resilience result not only from the physical form of the contact but also from the hardening efiect resulting from the coining operation by which the barrel halves are formed. These contacts are so eflective that it is relatively diflicult to remove the tube, although of course not impossible, so that special locking devices are not required.

' It will be appreciated that in attempting to attain sufliciently high tube retentivity the firstefforts to devise a contact for this purpose resulted in a contact requiring such a high tube insertion pressure, as to createa danger of breaking the glass vessel of the tube during insertion. This difficulty has been avoided in the contact here 'in disclosed.

The provision for compensation for manufacturing tolerances in devices of this type is enhanced not only by the spherical shape of the end of the barrels but by the fact that the slots SI and S2 and the slotted ball end are all aligned with the radius of the contact. As will be seen from Figure 1, these slots lie on the radius. of the circle on which the contacts lie. This feature facilitates insertion of the pin. The tube pins are commonly made of relatively soft wire and these structural features contribute to alignment of the pins with the contacts which alignment is 5 further enhanced by the fact that the contacts have no ears to clamp them rigidly between the insulating plates i and 2. Thus, by making the apertures through which the barrel 6 and the wings I extend slightly large the contacts can shift a small amount to further contribute to ease of insertion. The ball-shaped end of the contact I 9 is the chief contributing factor between the high ratio of pin insertion and pin extraction force. Finally, a structural feature of the invention is apparent from Figure 9 wherein, contrary to many previous types of contacts, the pin P does not engage the walls defining the barrel portion of the contact. The barrel portion is of relatively greater diameter than the pin P and the only engagement between the pin and the contact is at the engaging edges TB.

From the above description it will be apparent to those skilled in the art that the features of this invention while relatively specific are capable of some variation and it is desired therefore that the invention not be limited to the exact form of structure herein disclosed for purposes of 1 illustration but rather to the claim granted me.

What is claimed is:

An electrical contact comprising a pin receiving portion of tubular form, a connection wing extending in parallel relation thereto, said tubular portion being open at one end and hemispherically shaped at the other end, and an integral portion interconnecting the tubular portion at its open end to one end of said contact wing, the hemispherically shaped end of the tubular portion having an open slot, said hemispherical end having a pair of lateral notches at one end of and arranged on opposite sides of said slot.

q ALBERT W. FRANKLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

